- Homochiral BINAPDA-Zr-MOF for Heterogeneous Asymmetric Cyanosilylation of Aldehydes
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A new homochiral BINAPDA-Zr-MOF was prepared by a new chiral organic linker of (R)-4,4′-(6,6′-dichloro-2,2′-diethoxyl-[1,1′-binaphthalene]-4,4′-diyl)dibenzoic acid (R-L) and ZrCl4 under solvothermal conditions. Its structure was determined by P
- Jin, Fa-Zheng,Zhao, Chen-Chen,Ma, Hui-Chao,Chen, Gong-Jun,Dong, Yu-Bin
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p. 9253 - 9259
(2019/07/08)
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- Supported Ionic Liquid-Like Phases (SILLPs) as Immobilised Catalysts for the Multistep and Multicatalytic Continuous Flow Synthesis of Chiral Cyanohydrins
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Supported Ionic Liquid-Like Phases have been found to be efficient organocatalysts for the synthesis of cyanohydrin esters under solvent-free conditions by an “electrophile-nucleophile dual activation” based on hydrogen bond formation. The combination of
- Peris, Edgar,Porcar, Raúl,Burguete, María Isabel,García-Verdugo, Eduardo,Luis, Santiago V.
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p. 1955 - 1962
(2019/03/13)
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- Preparation of chitosan-supported urea materials and their application in some organocatalytic procedures
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An efficient and mild procedure was developed for the preparation of three chitosan-supported ureas containing electron-withdrawing groups. These catalysts were characterized and employed as organocatalysts in different transformations, including the enan
- de Gonzalo, Gonzalo,Franconetti, Antonio,Fernández, Rosario,Lassaletta, José M.,Cabrera-Escribano, Francisca
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p. 365 - 374
(2018/07/25)
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- High-Throughput Preparation of Optically Active Cyanohydrins Mediated by Lipases
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Cyanohydrins are versatile compounds with high applicability in organic synthesis; they are used as starting materials for the synthesis of other chemical targets with high industrial added value. Lipase-mediated kinetic resolution reactions are a promising route for the synthesis of optically active cyanohydrins. These reactions can be carried out through the acylation of cyanohydrins or the deacylation of cyanohydrin esters, with different biocatalysts and under different reaction conditions. Unfortunately, depending on the substrate structure, long reaction times can be required to achieve suitable enantiomeric excesses. In this context, we present a high-throughput protocol for the production of optically active cyanohydrins in continuous-flow mode. The products were obtained with moderate to good enantioselectivity (E values from 8 up to >200) and with productivity values from 2.4 to 8.7 times higher in continuous-flow mode than in batch mode. Moreover, the reaction times were reduced from hours in batch mode to minutes in continuous-flow mode.
- Thomas, Juliana Christina,Aggio, Bruno Bernardi,Marques de Oliveira, Alfredo Ricardo,Piovan, Leandro
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p. 5964 - 5970
(2016/12/26)
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- Dual Lewis Acid/Lewis Base Catalyzed Acylcyanation of Aldehydes: A Mechanistic Study
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A mechanistic investigation, which included a Hammett correlation analysis, evaluation of the effect of variation of catalyst composition, and low-temperature NMR spectroscopy studies, of the Lewis acid-Lewis base catalyzed addition of acetyl cyanide to prochiral aldehydes provides support for a reaction route that involves Lewis base activation of the acyl cyanide with formation of a potent acylating agent and cyanide ion. The cyanide ion adds to the carbonyl group of the Lewis acid activated aldehyde. O-Acylation by the acylated Lewis base to form the final cyanohydrin ester occurs prior to decomplexation from titanium. For less reactive aldehydes, the addition of cyanide is the rate-determining step, whereas, for more reactive, electron-deficient aldehydes, cyanide addition is rapid and reversible and is followed by rate-limiting acylation. The resting state of the catalyst lies outside the catalytic cycle and is believed to be a monomeric titanium complex with two alcoholate ligands, which only slowly converts into the product.
- Laurell Nash, Anna,Hertzberg, Robin,Wen, Ye-Qian,Dahlgren, Bj?rn,Brinck, Tore,Moberg, Christina
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p. 3821 - 3829
(2016/03/08)
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- Fast microwave-assisted resolution of (±)-cyanohydrins promoted by lipase from Candida antarctica
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Enzymatic kinetic resolution (EKR) of (±)-cyanohydrins was performed by using immobilized lipase from Candida antarctica (CALB) under conventional ordinary conditions (orbital shaking) and under microwave radiation (MW). The use of microwave radiation contributed very expressively on the reduction of the reaction time from 24 to 2 h. Most importantly, high selectivity (up to 92percent eep) as well as conversion was achieved under MW radiation (50-56percent).
- Ribeiro, Sandra S.,Ferreira, Irlon M.,Lima, Jo?o P. F.,De Sousa, Bruno A.,Carmona, Rafaela C.,Santos, Alcindo A. Dos,Porto, André L. M.
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p. 1344 - 1350
(2015/07/15)
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- Enantioselective cyanosilylation of aldehydes catalyzed by novel camphor derived Schiff bases-titanium(IV) complexes
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Five tridentate Schiff bases have been prepared from (1R,2S,3R,4S)-3-amino- 1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol and salicylaldehydes. X-ray structure investigation revealed differences in their molecular conformation, and their titanium(IV) complexes
- B?ocka, Ewelina,Bosiak, Mariusz J.,We?niak, Miros?aw,Ludwiczak, Agnieszka,Wojtczak, Andrzej
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p. 554 - 562
(2014/05/06)
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- Asymmetric cyanohydrin synthesis using an aluminium(salan) complex
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The asymmetric addition of trimethylsilyl cyanide to aldehydes catalysed by chiral metal(salan) complexes has been investigated. Salan complexes of titanium and vanadium displayed only low catalytic activity, but a bimetallic aluminium(salan) complex gave
- North, Michael,Stewart, Emma L.,Young, Carl
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p. 1218 - 1225,8
(2020/09/09)
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- Enantioselective O-acetylcyanation/cyanoformylation of aldehydes using catalysts with built-in crown ether-like motif in chiral macrocyclic V(V) salen complexes
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Chiral macrocyclic V(V) salen complexes 1a-f derived from macrocyclic ligands obtained by the reaction of 1R,2R-(-) diaminocyclohexane/(1R,2R)-(+)-1, 2-diphenylethylenediamine with bis-aldehydes 2 and 3 were synthesized and used as efficient catalysts in asymmetric cyanation reactions. The V(V) catalysts demonstrated excellent performance (product yields and ees up to 99%) with potassium cyanide (KCN) and sodium cyanide (NaCN). The catalytic system also performed very well with a safer source of cyanide-ethyl cyanoformate to give cyanohydrin carbonates in excellent yield and ee (up to 97%). The V(V) macrocyclic salen complex 1b retained its performance at multi-gram level and was conveniently recycled for a number of times.
- Khan, Noor-Ul H.,Sadhukhan, Arghya,Maity, Nabin C.,Kureshy, Rukhsana I.,Abdi, Sayed H.R.,Saravanan,Bajaj, Hari C.
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experimental part
p. 7073 - 7080
(2011/10/07)
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- Investigation of lewis acid versus lewis base catalysis in asymmetric cyanohydrin synthesis
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The asymmetric addition of trimethylsilyl cyanide to aldehydes can be catalysed by Lewis acids and/or Lewis bases, which activate the aldehyde and trimethylsilyl cyanide, respectively. It is not always apparent from the structure of the catalyst whether Lewis acid or Lewis base catalysis predominates. To investigate this in the context of using salen complexes of titanium, vanadium and aluminium as catalysts, a Hammett analysis of asymmetric cyanohydrin synthesis was undertaken. When Lewis acid catalysis is dominant, a significantly positive reaction constant is observed, whereas reactions dominated by Lewis base catalysis give much smaller reaction constants. [{Ti(salen)O}2] was found to show the highest degree of Lewis acid catalysis, whereas two [VO(salen)X] (X = EtOSO3 or NCS) complexes both displayed lower degrees of Lewis acid catalysis. In the case of reactions catalysed by [{Al(salen)}2O] and triphenyl- phosphine oxide, a non-linear Ham- mett plot was observed, which is indicative of a change in mechanism with increasing Lewis base catalysis as the carbonyl compound becomes more electron-deficient. These results suggested that the aluminium complex/tri- phenylphosphine oxide catalyst system should also catalyse the asymmetric addition of trimethylsilyl cyanide to ke- tones and this was found to be the case.
- North, Michael,Omedes-Pujol, Marta,Williamson, Courtney
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experimental part
p. 11367 - 11375
(2010/11/17)
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- Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate
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Propylene carbonate can be used as a green solvent for the asymmetric synthesis of cyanohydrin trimethylsilyl ethers from aldehydes and trimethylsilyl cyanide catalysed by VO(salen)NCS, though reactions are slower in this solvent than the corresponding re
- North, Michael,Omedes-Pujol, Marta
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experimental part
p. 1043 - 1055
(2011/03/22)
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- Asymmetric cyanohydrin formation from aldehydes catalyzed by manganese Schiff base complexes
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The catalyst generated in situ from Mn(OAc)2 and a chiral Schiff base ligand exhibited excellent catalytic abilities in asymmetric cyanohydrin formation from aldehydes with sodium cyanide in up to 99% enantioselectivity and good yield.
- Qu, Yanyang,Jing, Linhai,Wu, Zhiqing,Wu, Di,Zhou, Xiangge
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experimental part
p. 187 - 190
(2010/04/28)
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- Enzymatic kinetic resolution of racemic cyanohydrins via enantioselective acylation
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Enzymatic kinetic resolution of a series of aromatic and aliphatic cyanohydrins in organic media has been investigated. The behavior of potential lipases, molecular sieves, acyl reagent, reaction temperature, and organic solvents on the kinetic resolution was studied. The influence of substrate structure, steric, and electronic nature and position of the aryl substituent on the enantioselectivity was discussed. Under the optimized reaction conditions, good enantioselectivity could be achieved for most of the investigated compounds. Specifically, substrates 1a, 1c, 1d, 1f, 1u could be resolved with the kinetic enantiomer ratio (E) higher than 200.
- Xu, Qing,Xie, Yongli,Geng, Xiaohong,Chen, Peiran
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experimental part
p. 624 - 630
(2010/09/07)
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- Asymmetric synthesis of a new salen type-titanium complex as the catalyst for asymmetric trimethylsilylcyanation of aldehydes
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This work describes the asymmetric synthesis of a new salen-type ligand via a Diels-Alder reaction and Curtius rearrangement. The ligand with a norbornane skeleton was used in the trimethylsilylcyanation of aldehydes, but the enantioselectivity was 55%ee. The norborane skeleton was cleaved to destroy this rigidity, and the eanatioselectivity was thereby increased to 85%ee.
- Lin, Zheng-Chang,Chen, Chinpiao
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experimental part
p. 726 - 737
(2011/04/23)
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- Minor enantiomer recycling: Metal catalyst, organocatalyst and biocatalyst working in concert
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A minor enantiomer recycling one-pot procedure employing two reinforcing chiral catalysts has been developed. Continuous regeneration of the achiral starting material is effected via selective enzyme-catalyzed hydrolysis of the minor product enantiomer fr
- Wingstrand, Erica,Laurell, Anna,Fransson, Linda,Hult, Karl,Moberg, Christina
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supporting information; experimental part
p. 12107 - 12113
(2010/08/03)
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- A novel chiral (salen)AlIII complex catalyzed asymmetric cyanosilylation of aldehydes
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A novel chiral (salen)AlIII complex was synthesized through the reaction of Et2AlCl and salen (R,R)-1 derived from (R,R)-11,12-diamino-9,10-dihydro-9,10-ethanoanthracene. This complex is an efficient catalyst for the asymmetric trimethylsilylcyanation of aldehydes in the presence of tributylphosphane oxide as an additive. The use of 1 mol-% of the complex led to the corresponding cyanohydrins in high yields (85-94%) with good-to-excellent enantioselectivities (42-92%ee). Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Zeng, Zebing,Zhao, Guofeng,Zhou, Zhenghong,Tang, Chuchi
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experimental part
p. 1615 - 1618
(2009/04/11)
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- Enantioselective cyanosilylation of aldehydes catalyzed by a novel N,N′-dioxide-Ti(OiPr)4 bifunctional catalyst
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A novel bifunctional asymmetric catalyst containing N-oxide and titanium(IV) was developed and applied to the asymmetric cyanosilylation of aldehydes. Optically active trimethylsilyl cyanohydrin ethers were obtained up to 99% yield and 80% ee in the presence of 5 mol % catalyst loading at -78 °C. Based on the experimental results, the catalytic cycle was proposed as a pathway in which Lewis acid and Lewis base activated aldehyde and trimethylsilylcyanide (TMSCN), respectively.
- Zeng, Baiqing,Zhou, Xin,Liu, Xiaohua,Feng, Xiaoming
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p. 5129 - 5136
(2008/02/01)
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- Asymmetric synthesis of O-acetylcyanohydrins by reaction of aldehydes with NaCN/KCN catalyzed by recyclable chiral dimeric titanium(IV)/vanadium(V) salen complexes
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The efficient catalytic asymmetric addition of an inexpensive and nonvolatile cyanide source such as NaCN or KCN and acetic anhydride to various aldehydes was catalyzed by recyclable dimeric TiIV and VV chiral salen complexes at -20°
- Khan, Noor-Ul H.,Agrawal, Santosh,Kureshy, Rukhsana I.,Abdi, Sayed H. R.,Mayani, Vishal J.,Jasra, Raksh V.
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p. 3175 - 3180
(2007/10/03)
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- Asymmetric cyanosilylation of aldehydes catalyzed by novel organocatalysts
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A novel proline-based N,N′-dioxide, which is easily prepared from inexpensive chemicals, serves as an effective catalyst for enantioselective cyanosilylation of aldehydes in up to 73% ee. Georg Thieme Verlag Stuttgart.
- Wen, Yuehong,Huang, Xiao,Huang, Jinglun,Xiong, Yan,Qin, Bo,Feng, Xiaoming
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p. 2445 - 2448
(2007/10/03)
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- Dual Lewis acid-Lewis base activation in enantioselective cyanation of aldehydes using acetyl cyanide and cyanoformate as cyanide sources
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Dual activation by a chiral Lewis acid and an achiral or chiral Lewis base enabled cyanation of both aromatic and aliphatic aldehydes with acetyl cyanide and ethyl cyanoformate to provide direct access to O-acetylated and O-alkoxycarbonylated cyanohydrins
- Lundgren, Stina,Wingstrand, Erica,Penhoat, Mael,Moberg, Christina
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p. 11592 - 11593
(2007/10/03)
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- Enantioselective addition of trimethylsilyl cyanide to aldehydes catalysed by bifunctional BINOLAM-AlCl versus monofunctional BINOL-AlCl complexes
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A highly enantioselective cyanation of aldehydes takes place by using a bifunctional catalyst derived from 3,3′-bis(diethylaminomethyl) substituted binaphthol (BINOLAM) and dimethylaluminium chloride. The addition is of wide scope and runs best in toluene at temperatures ranging from -20 to -40°C, in the presence of 4 A? MS and triphenylphosphine oxide as additives. The (R)- or (S)-cyanohydrins result when using (S)- or (R)-BINOLAM-AlCl complexes, respectively. The valuable ligand can be recovered by simple extractive work-up and recycled without loss of efficiency (both in terms of chemical and stereochemical yields). This methodology is applied to the Shibasaki synthesis of epothilone A. All the evidence available for the BINOLAM-AlCl enantioselective addition of TMSCN to aldehydes call for the intervention of a hydrocyanation reaction, addition of a catalytic amount of hydrogen cyanide, generated in situ, to an aldehyde, followed by O-silylation. In order to determine the role of the basic amino groups of BINOLAM, comparative studies are carried out with the monofunctional 1,1′-binaphthol-derived complex BINOL-AlCl. Graphical Abstract.
- Casas, Jesús,Nájera, Carmen,Sansano, José M.,Saá, José M.
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p. 10487 - 10496
(2007/10/03)
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- Polymeric salen-Ti(IV) or V(V) complex catalyzed asymmetric synthesis of O-acetylcyanohydrins from KCN, Ac2O and aldehydes
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Polymeric salen-Ti(IV) and V(V) complexes were employed in the enantioselective O-acetyl cyanation of aldehydes with potassium cyanide and acetic anhydride. The crosslinked polymeric salen-Ti(IV) catalyst exhibited good activities and enantioselectivities, up to 91% ee with 99% conversion was obtained at -20°C with 1 mol% of catalyst (based on bimetallic catalytic unit). Moreover, six consecutive recyclings with the easily recovered crosslinked polymeric catalyst showed no obvious decrease in either activity or enantioselectivity. Linear polymeric salen-V(V) catalyst showed good catalytic efficiency too, up to 94% ee with 99% conversion was obtained at -42°C with 5 mol% of catalyst. Graphical Abstract.
- Huang, Wei,Song, Yuming,Wang, Jing,Cao, Guoying,Zheng, Zhuo
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p. 10469 - 10477
(2007/10/03)
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- Asymmetric addition of KCN and Ac2O to aldehydes catalyzed by recyclable polymeric salen-Ti(IV) complexes
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Polymeric salen-Ti(IV) complexes were employed in the enantioselective O-acetyl cyanation of aldehydes with KCN and Ac2O. The polymeric catalysts with appropriate crosslinking degree exhibited good activities and enantioselectivities, up to 94%
- Huang, Wei,Song, Yuming,Bai, Changmin,Cao, Guoying,Zheng, Zhuo
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p. 4763 - 4767
(2007/10/03)
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- Enantioselective synthesis of protected cyanohydrins
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A straightforward process for the preparation of optically active protected cyanohydrins, important building blocks for the synthesis of drugs and agrochemicals, has been established. Lipase B from Candida Antarctica (CAL-B) catalysed the kinetic resoluti
- Veum, Lars,Kuster, Marina,Telalovic, Selvedin,Hanefeld, Ulf,Maschmeyer, Thomas
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p. 1516 - 1522
(2007/10/03)
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- CAL-B catalyzed enantioselective synthesis of cyanohydrins - A facile route to versatile building blocks
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A straightforward process for the preparation of optically active cyanohydrins, important building blocks for the synthesis of drugs and agrochemicals, has been established. Lipase B from Candida antarctica (CAL-B) catalyzes the kinetic resolution of racemic cyanohydrin acetates under mild conditions: optimization of the process led to a user-friendly synthesis of (S)- and (R)-cyanohydrins.
- Hanefeld,Li,Sheldon,Maschmeyer
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p. 1775 - 1776
(2007/10/03)
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- Salen-Ti(OR)4 complex catalysed trimethylsilylcyanation of aldehydes
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Chiral selen-titanium complexes were found to be efficient catalysts for the enantioselective trimethylsilylcyanation of aldehydes. An enantioselectivity up to 87.1% e.e, was obtained by using 10mol% Ti(IV)-salen 2d as catalyst. The reaction mechanism was
- Jiang, Yaozhong,Gong, Liuzhu,Feng, Xiaoming,Hu, Wenhao,Pan, Weidong,Li, Zhi,Mi, Aiqiao
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p. 14327 - 14338
(2007/10/03)
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- One-Pot Synthesis of Optically Active Cyanohydrin Acetates from Aldehydes via Quinidine-Catalyzed Transhydrocyanation Coupled with Lipase-Catalyzed Kinetic Resolution in Organic Solvent
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A novel one-pot synthetic method was developed for the preparation of optically active cyanohydrin acetates.Racemic cyanohydrins were generated from aldehydes and acetone cyanohydrin by quinidine-catalyzed transhydrocyanation, and the resulting cyanohydrins 2a-j were then acetylated by lipase in a stereoselective manner using isopropenyl acetate as an acylating reagent.A variety of aldehydes 1a-j were successfully transformed into the corresponding cyanohydrin acetates 3a-j having 47-95percent e.e. without isolating the unstable cyanohydrins 2.Moreover, the reversible nature of base-catalyzed transhydrocyanation allows for in situ racemization of the unreacted cyanohydrins and concurrent kinetic resolution by lipase enabled the preparation of (S)-3b-d with 40-82percent e.e. in more than 50percent yield.Polymer-supported cinchona alkaloid was also used as a catalyst for this one-pot reaction and showed the comparable chemical and optical yield to that for the soluble monomeric alkaloid.The insoluble polymer and lipase were recovered by filtration and found to have almost the same catalytic activity even after four times of reuse.
- Inagaki, Minoru,Hatanaka, Akihiko,Mimura, Mitsuo,Hiratake, Jun,Nishioka, Takaaki,Oda, Jun'ichi
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p. 111 - 120
(2007/10/02)
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- One-Pot Synthesis of Optically Active Cyanohydrin Acetates from Aldehydes via Lipase-Catalyzed Kinetic Resolution Coupled with in Situ Formation and Racemization of Cyanohydrins
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A novel one-pot synthesis of optically active cyanohydrin acetates from aldehydes has been accomplished by lipase-catalyzed kinetic resolution coupled with in situ formation and racemization of cyanohydrins in an organic solvent.Racemic cyanohydrins 2, generated from aldehydes 1 and acetone cyanohydrin in diisopropyl ether under the catalysis of basic anion-exchange resin (OH- form), were acetylated stereoselectively by a lipase from Pseudomonas cepacia (Amano) with isopropenyl acetate as an acylating reagent.The (S)-isomer of 2 was preferentially acetylated by the lipase, while the unreacted (R)-isomer was continuously racemized through reversible transhydrocyanation catalyzed by the resin.These processes thus enabled one stage conversion of various aldehydes 1a-n into the corresponding (S)-cyanohydrin acetates 3a-n with up to 94 percent ee in 63-100 percent conversion yields.The racemization of the optically active cyanohydrin 2e by Amberlite IRA-904 (OH- form) was found to be much faster then the enzymatic acetylation, confirming the effective second-order asymmetric transformation.Enzymatic deacetylation of (S)-cyanohydrin acetates in an organic solvent and the synthesis of optically active pyrethroids are also described.
- Inagaki, Minoru,Hiratake, Jun,Nishioka, Takaaki,Oda, Jun'ichi
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p. 5643 - 5649
(2007/10/02)
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- Enzymatic Preparation of Optically Active Cyanohydrin Acetates
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A series of cyanohydrin acetates (1)-(47) of widely varying structures, potential chiral building blocks for numerous synthetic applications, has been prepared in good chemical and often high optical yields by enzymatic hydrolysis of their racemic acetates in the presence of an ester hydrolase from Pseudomonas sp.
- Almsick, Andreas van,Buddrus, Joachim,Hoenicke-Schmidt, Petra,Laumen, Kurt,Schneider, Manfred P.
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p. 1391 - 1393
(2007/10/02)
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